Technical Field
The present invention relates to a pipe member used for a heat pipe, a heat pipe using such pipe member, and a cooling device.
Related Art
Conventionally, a heat pipe is known as a member for transferring heat from a heat receiving part to a heat radiation part when cooling a heat generating component. The heat pipe encloses a working fluid inside the pipe member and transfers heat by the movement of the working fluid.
Among the heat pipes, there is known a type with which a part thereof is heated by the heat received at the heat receiving part, the working fluid is evaporated inside thereof to be in a gas phase, and the heat is transferred with latent heat transport by the movement of the gas phase (e.g., see Japanese Patent Laid Open Publication No. H09-126672). Further, among the heat pipes, there is also known a type with which the working fluid moves in a mixed state of a liquid phase and a gas phase, and latent heat transport by the movement of the gas phase and sensible heat transport by the movement of the liquid phase are executed simultaneously (e.g., see Japanese Patent Laid Open Publication No. 2013-160420).
The heat pipe depicted in JP 2013-160420 is called as a self-oscillating heat pipe since it utilizes self-oscillation generated when the liquid phase is heated and nucleate boiling is caused for moving the working fluid. The self-oscillating heat pipe is drawing an attention since heat transport is carried out with both latent heat transport and sensible heat transport so that it is capable of dealing with heat transport of a large heat flux.
FIGS. 9A and 9B show schematic and block diagram views of a conventional self-oscillating heat pipe. FIG. 9A shows a schematic view of a self-oscillating heat pipe 500, and FIG. 9B shows a block diagram showing behavior of a working fluid 520 in the self-oscillating heat pipe 500.
The self-oscillating heat pipe 500 shown in FIGS. 9A and 9B encloses the working fluid 520 that is a mixture of a liquid phase 521 and a gas phase 522 inside a pipe member 510 formed in a loop-like shape. In the self-oscillating heat pipe 500, heat is transported between an evaporation part 501 where the working fluid 520 evaporates due to a phase change by applying heat and a condensation part 502 where condensation occurs due to a phase change by radiating heat. A part of the pipe member 510 of the self-oscillating heat pipe 500 is shaped in a zigzag form by reciprocating between the evaporation part 501 and the condensation part 502 for a plurality of times.
In the evaporation part 501, thermal expansion of the gas phase 522 occurs and air bubbles generated by nucleate boiling promote expansion of the gas phase 522 so that the pressure is increased. Meanwhile, in the condensation part 502, the pressure is decreased due to condensation of the gas phase 522. Then, due to a pressure difference between the both and pressure shock caused by the nucleate boiling in the evaporation part 501, the liquid phase 521 self-oscillates as shown with an arrow D51 in FIG. 9A.
As a result, as shown with an arrow D52 in FIG. 9A, the gas phase 522 moves from the evaporation part 501 to the condensation part 502. By the movement of the gas phase 522 with expansion and condensation thereof, latent heat transport from the evaporation part 501 to the condensation part 502 is carried out.
Further, the liquid phase 521 self-oscillates between the evaporation part 501 and the condensation part 502 to repeatedly execute heating in the evaporation part 501 and cooling in the condensation part 502. Also, along with the movement of the gas phase 522, the liquid phase 521 moderately circulates inside the loop-like pipe member 510 so that heating and cooling are repeatedly executed by the circulation as well. Such self-oscillation and circulation with heating and cooling of the liquid phase 521 executes sensible heat transport from the evaporation part 501 to the condensation part 502.
By the behavior of the working fluid 520 described above, latent heat transport by the gas phase 522 and sensible heat transport by the liquid phase 521 are simultaneously executed in the self-oscillating heat pipe 500.
However, the self-oscillating heat pipe 500 described above needs to form the pipe member 510 in a loop-like shape for circulating the working fluid 520. Therefore, installation thereof may become difficult depending on the shape of the installation place.
Meanwhile, the type of heat pipe depicted in JP H09-126672 with which the heat is transferred only with latent heat transport does not need to form the pipe member in a loop-like shape. With this type of heat pipe, one end of a bar-like pipe member serves as an evaporation part and the other end serves as a condensation part in many cases. The gas phase generated by evaporation in the evaporation part moves to the condensation part and returns to the liquid phase. The liquid phase needs to be flown back from the condensation part to the evaporation part to be ready for next evaporation. Therefore, on the inner face of the pipe member of the above-described type of heat pipe, minute uneven shapes called wick for introducing the liquid phase to the evaporation part by utilizing capillarity or gravity are formed in many cases. The liquid phase flows back from the condensation part to the evaporation part via the wick.
Since such type of heat pipe does not need to form the pipe member in a loop-like shape, it seems to be highly flexible in terms of installation thereof. However, it is required to have the above-mentioned wick or the like, for example, in the pipe member. Particularly the wick cannot function to help flow-back when the uneven shapes are crushed, so that it may be an obstruction for bending or the like of the pipe member into desired shapes. Therefore, even the type of heat pipe with which the heat is transferred only with latent heat transport may become difficult to be installed depending on the shape of the installation place.
It is therefore an object of the present invention to pay attention to such issues and to provide a pipe member capable of configuring a heat pipe that can be installed with high flexibility in accordance with the state of the installation place and to provide a heat pipe configured by using such pipe member and a cooling device.